and the Effects of Glacial Action. 293 



which produced the higher scratches. But we think it in- 

 cumbent upon them to tell us what was the velocity of the 

 stream which could raise and keep, for perhaps a horizontal 

 distance of six feet, a block of porphyry or basalt, even a few 

 inches above the bed of the river. 



There is another point which the opponents of the glacial 

 theory would do well to consider — the agent which has 

 produced all the earthy materials of soil. If the mouldering 

 of rocks by the influence of the atmosphere, and the sup- 

 posed abrasive power of water, have been the principal agents 

 engaged, milliops of years would not have suflBced to produce 

 the soil which covers the smallest of the English counties. 

 The Falls of Niagara afford an admirable illustration of the 

 effects of water ; and perhaps no example could be found 

 more favourable to the views of the advocates for the abrasive 

 power of water, if such a power exists. It is conjectured, 

 and apparently with much truth, that the Falls were once at 

 Queenston, about seven miles down the river, and that they 

 are slowly receding up the river.* Mr Lyell thinks the 

 rate of recession may be estimated at a foot annually, and, 

 consequently, that it is 35,000 years since the Falls were at 

 Queenston. According to the same author, the ravine in 

 which the river flows, is at the Falls cut perpendicularly 

 through 80 feet of limestone rock, and through the same 

 thickness of shale; and at Queenston it is cut through 100 

 additional feet of sandstone. Now, the depth of the Falls is 

 about 1(35 feet ; and assuming that the average breadth of 

 the ravine between the Falls and Queenston is 3000 feet, 

 (which is more than the width of the two falls,) and that 

 Queenston is 100 feet below the level of the bottom of the 

 Falls, 2649 millions of cubic yards of rock have been exca- 

 vated to form the ravine ; or, in 35,000 years only as much 

 material has been removed as would cover a space 30J miles 

 long and four broad, seven yards thick. But the whole of 

 the excavated material would not be sand or abraded rock ; 

 much of it would be detached in considerable masses ; and 



* Travels in Annerica. 

 VOL. XLII. NO. LXXXIV. APRIL 1847. 



